The present invention relates to a flexible membrane spherically designed for heavy duty apparatus and, in particular, for apparatus operating in sterile environments, comprising a corrosion resistant sheet body provided with high strength mechanical characteristics both at low and high temperatures, possibly provided with one or more regions or region sets suitably shaped and adapted for easily deforming, which body is rigidly and tightly restrained at its outer and inner peripheral edges. On a side of this body there are arranged a plurality of annular concentric bodies which may slide with a coaxial relationship, and which are held in their positions adhering to said sheet body by means of radially extending pins the rounded ends or which engage in peripheral seats formed on fixed and movable bodies therebetween said sheet body is arranged.
As is known, in many industrial fields and, in particular in the chemical, drug and food industries, the processed products must constantly be held in sterile environments.
To this end a lot of apparatus have been designed and constructed able of providing the mentioned sterile conditions; in particular these conditions are obtained in autoclaves, in pressurized vessels and ducts: however, as it should be apparent to those skilled in the art, these sterile conditions can be hardly obtained in apparatus such as valves, pressure gauges, metering devices and the like.
In order to solve these problems in the latter apparatus tight pads and specifically designed resilient membranes have been already made, by using materials such as teflon and/or stainless steel.
In connection with thementioned tight pads it has been found that the valve driving stems, even if sheated in a very precise way, by using tightness rings adhering both to the walls of the valve bodies and to said stems, are not able of providing the required sterile conditions.
The elastic membranes, on the other hand, have provided remarkably better results, as shown, for example, in the Italian Patent Application No. 46,829 A/85 filed on Apr. 24, 1985 in the name of the same Applicant as the present invention.
However, under given conditions, the mentioned known elastic membranes have not been found to be able of resisting against heavy operation conditions.
This occurs mainly as, for given applications, there are used devices such as valves, metering apparatus and the like having rather long opening and closure strokes, and/or which must operate under a high pressure and/or a high temperature.